a) Field of the Invention
The present invention relates to an insulative fixing plate damaged when overheating as well as a plug and a socket using that insulative fixing plate. The insulative fixing plate damaged when overheating is a fixing element for combination and enables two conductive elements to be limited from contacting with each other, thereby forming a closed path. In addition, the insulative fixing plate is damaged when overheating, which allows the two conductive elements to be opened with respect to each other by an elastic force, thereby forming an open circuit. According to the present invention, the insulative fixing plate damaged when overheating, is further used in overheat protection for a plug or a socket.
b) Description of the Prior Art
To prevent a circuit from current overloading, short-circuit or overheating, the circuit will be usually provided with a fuse or a breaker. When the circuit temperature is too high or the current is too large, the fuse will be melted down by high temperature or the metal spring leaves of the breaker will be ejected, which forms an open circuit to power off the circuit, thereby securing the safety in using electricity.
For the prior art related to the fuse structure, there is a Taiwanese Invention Patent Publication No. I371053, “Thermal Fuse Connecting Structure.” The invention includes primarily two terminals which are connected together to form a closed path, and a hot-melt metal which is combined on the two terminals. When the circuit current is overloaded, the circuit is overheated or the environmental temperature under which the circuit is used is too high, the hot-melt metal will be melted and broken by the rise of temperature due to heat-up, so that the two terminals will not be connected with each other, thereby forming an open circuit state.
However, the hot-melt metal disclosed in the prior art is a conductive material; therefore, when the hot-melt metal is melted and broken, if part of residual of the hot-melt metal is attached on the two terminals, then that residual of the hot-melt metal can easily result in miss contact between the two terminals, thereby being unable to power off the circuit completely. On the other hand, the melted and split hot-melt metal can be ejected off by the two terminals that are opened with respect to each other to form an open circuit, and thus collide with other object to form miss contact, causing short-circuit. Accordingly, it is still dangerous in using that invention.
In order to deal with that issue, a Taiwanese Utility Model Patent No. M477079, “Overheat Failure Safety Structure and a Plug and a Socket with the Overheat Failure Safety Structure,” was disclosed. This patent claims an insulative limiting element which connects two conductive elements to form a closed path. When the circuit is overheated, the insulative limiting element will be melted and broken, allowing the two conductive elements to be opened with respect to each other by an elastic force to form an open circuit. The limiting element is provided with a first insulative part and an opposite second insulative part. A connecting part is used to connect the first insulative part with the second insulative part, forming a U-shaped appearance and having an open end. The two conductive elements are clamped tightly at the open end.
Upon practically using that patent, the present inventor has found out that as the U-shaped limiting element may not have sufficient rigidity of combination, even the closed path between the two conductive elements is not overheated, the binding force of the U-shaped limiting element can be still reduced due to heat-up and the limiting element can be ejected off by the elastic force between the two conductive elements, thereby forming an open circuit between the two conductive elements. On the other hand, when the temperature between the two conductive elements is too high, the first insulative part and the second insulative part of the U-shaped limiting element will be ejected off by the elastic force between the two conductive elements. However, as the connecting part is still connected at the first insulative part and the second insulative part, the U-shaped limiting element will maintain a part of the binding force, so that the two conductive elements will keep partly contact, thereby being unable to power off the circuit completely. All the two situations described above are the possible false actions.